Connector assemblies for severe environments are typically held in mating engagement by a clamp ring of one connector portion threadingly engaging the mating connector portion. Traditionally, the clamp ring is held in its clamping state by having the ring configured with a single lead thread having a pitch of about 20 threads per inch, and by the use of safety wire. More recently, coarser and/or multiple-lead threads have been preferred for permitting rapid coupling and uncoupling of the assemblies. Connectors of this type include those known as “Series III” connectors that are specified in standard shell sizes 9-25 for many high-performance applications according to MIL-C-38999/26D (dated May 7, 1990).
When Series III connectors are subjected to heavy vibration, it is required that the mating portions maintain a solid metal-to-metal face contact. It is also required that the performance under vibration be maintained even after a certain minimum number of complete engagements and disengagements of the mating portions. For this purpose, some form of locking device is provided for the clamp ring. One form of locking device presently in use includes a set of ratchet teeth that project outwardly from a first shell member, one or more detent members being carried on respective spring members by a threaded clamp ring that is rotatably connected to the first shell member. Rotation of the ring in a clamping direction for clamping to a second shell member is accompanied by ratcheting of the detent members over the teeth, the teeth each having a moderately inclined first ramp surface that resists the clamping direction of rotation. Also, each of the teeth has a more steeply inclined second ramp surface that heavily resists rotation of the ring in an opposite, unclamping direction.
Prior art connectors are typically subject to one or more of the following disadvantages:
1. The locking device is ineffective in that it does not maintain the required solid metal-to-metal face contact in that the discrete detent positions do not necessarily lie in phase with the fully clamped position of the ring such that even a slight vibration can cause the ring to back off slightly, the face-to-face contact being immediately lost when pressure is released from a compressively loaded elastomer that typically seals contact pins of the connector;
2. The locking device is ineffective in that the detent members do not prevent continued rotation in the unclamping direction, particularly after a number of engagement cycles, because the detent members have very little contact surface area, rapidly wearing away the teeth; and
3. The locking device is unreliable in that harmful foreign matter is not excluded, being damaged when the connector is decoupled, such as when water freezes within the device.
A variation of the above-described prior art locking device has the detent members formed in pairs that are slightly out of phase for providing detent positions in a multiple of the number of teeth. Each pair of the detent members is located on a multiply supported counterpart of the spring member, designated, the spring member rocking slightly on a middle support, one of the detent members moving inwardly as the other moves outwardly between detent positions. This prior art configuration suffers from each of the above disadvantages except to the extent that the greater number of detent positions limits the backing off of the clamp ring to the first detent engagement. A further disadvantage of the configuration is that it is more expensive and complicated to assemble in that a multiple complement of the detent members is required for obtaining the same locking torque.
Yet another variation of the first above-described prior art locking device has the teeth projecting axially from a counterpart of the first shell member. Several of the detent members (typically four or six) are formed on an annular detent plate that has outwardly projecting tabs for keyed engagement with a counterpart of the clamp ring. The detent members are axially biased against the teeth of a wavy spring member. The spring member is supported within the clamp ring by a first retaining clip. A second retaining clip clamps against the first shell member opposite the teeth when the ring is advanced in the clamping direction of rotation. This prior art configuration, while failing to overcome the disadvantages of the previously described prior art configurations, has other serious problems. For example, the clamp ring must overcome the axial force from the spring member in addition to the other sources of resistance to clamping of the mating connector portions. Conversely, the spring member continuously urges the mating portions apart, hastening failure of the connector. Also, the retaining clips are considered to be unreliable, failure of the clip catastrophically rendering the clamp ring completely ineffective in holding the connector in its mated condition. Further, the spring member makes only spaced apart contact with the detent plate, typically at from three to six locations, subjecting the relatively thin plate to undesirable bending deflections between the spaced apart detent members that produce uncontrolled variations in the biasing forces, and possible failure of the detent plate by fatigue.
U.S. Pat. No. 5,199,894 (“the '894 patent”) describes a locking device which represents a marked improvement over the aforementioned prior art. This patent, the contents of which are incorporated herein by reference, discloses a system for locking and unlocking a connector pair having a threaded clamping nut or ring that is rotatably coaxially supported on a first shell body for holding connector contacts in axial engagement. A multiplicity of first detent members angularly fixed relative to the clamping ring engage a corresponding multiplicity of second detent members fixed to the first shell body, and a cone-shaped spring washer axially holds the members in facing engagement, whereby a total surface contacting area of engagement between the detent members is at least 0.1 times the product of an average engagement pitch diameter and the width of engagement. The first and second detent members can engage at shallow contact angles of not more than about 40 degrees. The spring washer contacts the first detent ring, which can axially slidably engage an engagement surface fixed to the clamping ring, along a continuous annular contact path for uniform axial biasing of the detent members. The connector preferably includes an adjustment ring threadingly engaging the clamping ring for adjustably preloading the spring washer. The clamping ring is preferably axially movable relative to the first shell body between open and closed positions having associated spring biasing levels that contribute positively to an overall clamping force between mating connector portions. The connector also includes resilient O-ring members frictionally connecting the clamping ring and the first shell body for dampening vibrations therebetween, and for sealingly enclosing the detent members and the spring washer.
The reliance of the connector of the '894 patent on the use of the resilient O-ring members increases the expense and complexity of manufacturing the connector due to the necessity for very narrow tolerances in the dimensions of the O-ring members.
Also, the connector of the '894 patent requires the user to carefully adjust the tension on the spring washers by precisely adjusting the threaded end cap. Such requirement for careful adjustment of the tension on the spring washer is a problem for the manufacturer of the connector. If the tension on the spring washer is adjusted too high or too low, the connector will not meet specifications, will fail to function properly and will result in undue quantities of rejections.
Thus there is a need for a connector having a locking device that overcomes the above disadvantages.